Familiarity Breeds Humanity: Humans Can Better Categorise Dog (Canis familiaris) than Chimpanzee/Bonobo (Pan troglodytes/Pan paniscus) Facial Displays of Emotion

Human beings are highly familiar over-learnt social targets, with similar physical facial morphology between perceiver and target. But does familiarity with or similarity to a social target determine whether we can accurately infer emotions from facial displays? Here, we test this question across two studies by having human participants categorise facial displays of emotion from dogs, a highly familiar social target but with relatively dissimilar facial morphology, and chimpanzees, an unfamiliar social target, but a close genetic relative with a more similar facial morphology. We find that people are more accurate categorising facial displays of emotion from dogs compared to chimpanzees. However, we also find an effect of emotion, such that people vary in their ability to recognise different emotional states in different species, with anger more recognizable across species, perhaps hinting at an evolutionary bias towards detecting threat. These results provide initial evidence that familiarity or experience with a non-human animal affect reading emotion from facial displays.